In existing mobile (cellular) communication systems, network operators typically seek to optimise their network coverage based on measurements compiled during so called drive tests. Specifically, an operator can have a technician drive a vehicle around the network using specialist equipment to measure performance from a subscriber's perspective. The equipment typically comprises a special test mobile communications device and a wideband scanner, connected to data logging and analysis equipment such as a portable computer. Some drive test equipment is configured for remote operation, thereby allowing equipment to be placed in fleet vehicles (such as taxis, buses, delivery vehicles or the like), for automatic data collection.
Drive tests provide a good source of RF data, in association with related geographic positional information that can be used to identify and resolve coverage problems or the like. However, measurements can be time-consuming, expensive to perform, and often do not accurately represent the experience of a real pedestrian user, such as a user in a building or at a significant distance from a road. Moreover, with the extensive geographical coverage of mobile communication networks, drive tests can result in significant emissions of CO2 with the well known associated environmental issues.
Accordingly, the 3rd Generation Partnership Project (3GPP) proposed the development of automated solutions, including the involvement of mobile communication devices (User Equipment (UE)) in the field, in order to minimise operator costs, and the environmental impacts, of network deployment and operation. Studies carried out in response to this proposal demonstrated the feasibility of implementing procedures for minimising the need for drive tests (referred to herein as ‘Minimisation of Drive Tests’ or ‘MDT’ procedures, but also known as ‘management of UE based network performance measurements’), in which the UE takes measurements for use by the network to improve network optimisation and efficiency. More specifically, these studies demonstrated the feasibility of using control plane solutions for acquiring the measurements from devices. This information, together with information available in the radio access network can then be used for coverage optimisation purposes.
In current proposals for MDT procedures, a MDT capable UE is initially configured to perform MDT measurements by the network. On configuration, the MDT capable UE sends detailed user location information comprising, for example, GNSS (Global Navigation Satellite System) data (if available) and/or Radio Frequency fingerprints, along with the reported UE measurements, when requested to do so by the network. This detailed user location information is particularly useful for MDT as it allows an operator accurately to associate the geographical location of the user, within a particular radio cell, with the associated radio measurements; thereby allowing network coverage issues (e.g. coverage holes) to be located accurately.